Gantry crane?

[hex0rz]

Alright, so one of my goals within this year is to make a gantry crane. I have been wanting one for a while now. Biggest thing is being able to hang large game for skinning and quartering. It will obviously serve many different purposes other than hanging game. The possibilities are endless.I want to make it large enough to stand higher than my truck and wider so I could back through it. I estimated it to be at the dimensions of 10'x12'. Giving me some room to clear the mirrors/open doors and tall enough to have clearance and some play room if needed. Then, as far as winching goes, the best would be to go motorized.Design is easy. A-frame style. But material is my biggest concern. I want to make something that can handle lifting a tank! I was trying to think of being able to just lift a cord of wood right out of the bed with it. Except, a cord of green wood can easily reach 6-8k lbs! Depending on species...I would really like to build it out of strong lumber. I have not priced out how much metal or lumber would be, but lumber would be cheaper than steel. Although, steel is stronger.If anyone here can give me an idea on strength on lumber, it would be helpful. Engineering one out of steel is a no-brainer for me. Engineering one out of lumber is a little more difficult. Here are my thoughts on how to try and structurally engineer one out of lumber. Granted, I would have to accept the fact I would never be able to lift a cord of green wood out of the bed, but thats okay if I can other serious stuff.Building off the A-frame method, all of it would be made out of the largest beams I could get my hands on. Such as something like 12x12's or something. The top running section would be composed of 4 of these in a square like shape. Then, putting all them together, I would drill holes and fasten using 3/4" threaded rod. The top running section would have these pieces of all-thread running from side to side, and then top to bottom, so all 4 are joined to each other.Maybe if thats not strong enough, plate the weakest points with 1/4" steel? What do you guys think? Would it be feasible and work? Should I do treated or non-treated lumber? If non-treated, paint it or seal it? I would do my best to keep it in an enclosed area so it is not beaten down by the weather/sun, but it would probably have to come out some of the time. I know UV can really give wood a beating just as much as humidity can.

[flagmanruss]

I thought you were talking about something BIG!

My Acme Marine Hoist c1980

[hex0rz]

You'll let me borrow that, right?

[flagmanruss]

I miss those days, for sure.It was interesting driving when you couldn't see the other side... like rolling out on the narrow piers. The operator's station was on the other box beam about mid way. All powered by a slant 6 through hydraulics! Those massive tires were commercial aircraft rubber.

[hex0rz]

So, I take it nobody has ever built a gantry crane? No one on here is an engineer? Nothing?

[War Eagle]

I have built one but not out of wood like you are asking and not for the weight you are asking about.I used steel posts and steel I-beam with an 'A' frame setup on roller wheels so it can be moved around.Designed for 2-3000 lbs with adjustable height an 8 foot span.You are asking about a boat load of weight on a wood structure.Not what I would want to do.

[anoldbiker]

I would also check with your states laws. Some states make it mandatory for minimum standards. Privately owned or not, liability can be an issue if damage / injuries occur. The design specs can be an issue also. Your not talking about something like an engine lift, it WAY bigger.As for designing one, nothing by a web search ?

[hex0rz]

E-mailed an engineer on the issue. Asked about I-beam size for 5ton capacity at 10 a foot span. Guess I'll see what he says. Got a quote on an I-beam at those dimensions in a 12". 35lbs. a foot and it came out to like $340.Not bad, considering the harbor freight gantry crane offered is $700 and can only handle 1ton. Dunno what the 12" I-beam I got a quote on can handle, but I bet it could handle more...Sounds like I could get a pretty decent one made up for cheaper...